1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method that are suitable to a color management processing or the like to reproduce desired colors in a high dynamic range (HDR) display employing a dual modulation system.
Priority is claimed on Japanese Patent Application No. 2004-269674 filed Sep. 16, 2004, and Japanese Patent Application No. 2005-165202, filed Jun. 6, 2005, the contents of which are incorporated herein by reference.
2. Description of Related Art
In a dual modulation system, an additional modulation system is placed in optical series with a typical single modulation system. Accordingly, a color management processing adapted to the conventional single modulation system cannot be used for a display apparatus employing such a dual modulation system. To address this issue, various solutions have been proposed.
One conventional technique disclosed in Japanese Patent No. 3523170 is a dual modulation system in which a modulation light source is used as one of the modulation systems. The mechanism to modulate the light source employs a combination of a normal illumination using a cold-cathode tube and a modulation illumination by means of white light-emitting diodes (LEDs). Thus, the chromaticity of light from the light source changes in response to the modulation due to the differences in the emission spectra of the cold-cathode tube and the white LEDs. This change in the chromaticity is formulated into the following equation (2). The equation (1) is a transformation formula when normal illumination is provided using the cold-cathode tube.(X,Y,Z)t=M(R,G,B)t  (1)(X,Y,Z)t=M(R,G,B)t+gM′(R,G,B)t=N(R,G,B)t  (2)N=M+gM′  (3)
where R, G, and B represent RGB signals; X, Y, and Z are tristimulus values, M is a 3×3 linear conversion matrix when normal illumination is provided using the cold-cathode tube, M′ is a 3×3 linear conversion matrix when illumination is provided using the white LEDs, and “g” is a constant (gain, i.e., a value determined depending on the luminance level of the white LEDs).
However, the equation (3) cannot be used for a case in which the chromaticity changes in response to the modulation, as in the case in which the additional modulation element is a liquid crystal panel, for example. Furthermore, when the modulation takes place using a liquid crystal panel in place of the above-described modulation light source, for example, the chromaticity change exhibits a non-linear behavior, which cannot be expressed by a simple variable such as gM′ that represents the white LEDs in the above equation (2).